This invention relates to a system for conserving energy in the operation of a motor vehicle in which the fuel supply to the vehicle is controlled by a foot pedal. It is well known that if the operator can be constrained to operate the vehicle at a speed not greater than the national speed limit of 55 miles per hour, there will be a great savings in fuel. This is because the fuel consumption at speeds over 55 miles per hour is much greater than at 55 or lower. It has also been determined that there are fewer injuries and fatalities resulting from accidents at speeds of 55 miles per hour or less.
In the past, speed control devices have been proposed for motor vehicles. These have included adding an additional spring to resist depression of the foot pedal at a set speed after which the pedal resistance is increased as the spring is compressed. Because the apparatus is actuated at different pedal positions the operator can manipulate the pedal to obtain engagement at an artificially depressed position of the pedal such as when the vehicle is going up hill or being accelerated rapidly. Thereafter the spring force resisting depression of the pedal may be minimal because the amount of pedal depression required to travel at speeds over the speed limit is less than the pedal depression at which the spring is engaged.
In addition, even if the spring is engaged in a normal manner at the speed limit and on a level road, the resistance to pedal depression is a function of the spring rate and not the vehicle speed. Therefore if the spring rate or force per inch of spring retraction is great at speeds slightly in excess of the speed limit to reduce marginal speeding, the force required to go over higher speeds will be so great the operator will not have the strength to depress the pedal and cause the vehicle to travel at high speeds. This creates a safety hazard in that the operator will not be able to operate the vehicle at high speeds in an emergency to avoid an accident. On the other hand, if the spring rate is low enough to permit depression of the pedal at high speeds, it may not be sufficient to provide initial high resistance to depression of the pedal at velocities in the lower part of the speed range. This apparatus may also be tampered with by the operator to remove or reduce the constraining force which is not desirable.
In other speed control devices, warnings are given the operator when the speed limit is reached; however, no appreciable resistance is provided to constrain the operator from operating the vehicle at speeds over the speed limit. Some speed control devices have vacuum and/or spring resistance to pedal depression which is applied at a certain speed; however, there is no correlation between the speed of the vehicle over the speed limit and the resistance to pedal depression.